The present invention relates to cutter apparatus for use in cutting paper tubes. These tubes are made from spirally wound paper tape. During their manufacture, they are fed axially along an arbor, and when the tube reaches a sufficient length, it is desirable to cut the tube. Such tubes have many different uses in various industries. For example, in the electronics industries, paper tubes are used as coil forms.
In order to facilitate cutting of the paper tubes, the tubes are normally pulled off the arbor after forming, and they are suspended or cantilevered off the end of the arbor so that a saw or cutting element does not strike the arbor during cutting.
For tubes of larger size, there is enough rigidity in the tube itself to trip a switch or otherwise actuate the cutter mechanism. However, for tubes of smaller diameter with thin walls (for example, 1/2 in. or smaller in diameter and 0.005 in. or less wall thickness), the length of tubes suspended off the arbor may reach 30-36 inches, and the tube has a tendency to wobble or vibrate. It is therefore difficult to actuate a switch or to sense the end of the tube optically (especially in the case of clear tubes), as is sometimes done in the case of larger, more rigid tubes.
Another problem with tubes of smaller size is that it is difficult and uneconomical to cut them with saw blades, and conventionally, a cutter blade is actuated cyclically, and independently of the feed rate of the tubes. Any variation in the cycle rate of the cutter or the feed rate of the tubes, or both, will result in variations in tube length, and this produces larger waste since the tubes are normally cut at a longer length during manufacture, and then cut to the ultimate desired length after shipment at the longer length.
According to the present invention, a sensor plate of large area but light in weight is arranged in a plane transverse of the axial direction of the tube, and adapted to be engaged by the suspended free end of the tube. The area of the plate is large enough so that even if the free end moves or vibrates, it will not escape engagement with the sensor plate. A support which drops away when the tube is cut helps hold the tube in place prior to and during cutting.
When the sensor plate is engaged by the tube, further movement of the tube will cause the free-hanging plate to interrupt a light beam to generate a signal which energizes a motor and also actuates a timer. The timer is set to time out in a predetermined time less than a complete cycle of a snap cutter. When the timer times out, the motor is disengaged, and it is a braking motor so that it stops almost immediately. However, an overriding directional clutch is inserted between the shaft driven by the motor and the cutter knife so that the cutter knife is free to complete its cycle and is returned to its original position where a cam stops it. Thus, the system is ready for a next cut.
The cutter blade is spring-mounted on an arm secured to a disc which is driven through a complete cycle when the motor is energized. When the cutter blade rides over the stop cam and clears it, the spring causes the cutter blade to accelerate substantially, thereby effecting a clean, sharp cut of the tube. After the cutter cleans the tube (approximately 200 angular degrees of rotation of the disc), the timer deenergizes the motor, and the inertia of the disc causes the overriding clutch to return the cutter blade to its initial position.
The present invention thus provides a convenient, economical and reliable snap cutter useful in the production of paper tubes of small sizes.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.